The present invention relates to laminated films each constituted by at least two layers. More particularly, the present invention relates to laminated films having flexibility, mechanical strength, transparency, surface wettability, low-temperature sealability, etc., which are each a soft film comparable to a soft vinyl chloride resin film and a vinylon film.
In recent years, soft vinyl chloride resin films containing a plasticizer have been widely used as a soft resin film. Soft vinyl chloride resins, however, may give rise to social problems such as (1) toxicity caused by bleed-out of plasticizer of monomer used therein, (2) transition and (3) acid rain derived from hydrogen chloride generated by burning thereof.
Meanwhile, as a soft resin film similar to the soft vinyl chloride resin films, there are resin films using ethylene as a main component, such as ethylene/vinyl acetate copolymer film, low-density polyethylene film, ionomer film and the like. These ethylene-based soft resin films, however, are inferior to soft vinyl chloride resin films in transparency, haze, gloss, etc. and moreover have poor impact strength, heat resistance, and stiffness.
A vinylon film widely used for fiber packaging has an excellent feeling of flexibility but, unlike polyolefin films, is extremely costly.
Meanwhile, in crystalline polypropylene films, it is conducted to impart flexibility while maintaining their transparency and haze, by using a propylene random copolymer of reduced melting point obtained by randomly copolymerizing propylene and ethylene and/or an .alpha.-olefin. With any existing technique, however, it is difficult to allow a crystalline polypropylene resin to have a flexibility comparable to that of soft vinyl chloride resin.
In view of the above situation, the present invention is intended to provide a resin film which has good transparency, haze, gloss, etc., which has excellent flexibility and mechanical strength, and which has good impact resistance, surface wettability, low-temperature sealability, etc.
The present invention is also intended to provide a resin film suitably used, because of the above properties, in various applications, for example, a packaging film on which multi-colored decorative printing has been made (e.g. food-packaging film, fiber-packaging film), a transfusion bag and intravenous bag film used in medical care field, a metal-protecting film, an adhesive film, and a building material film used in civil engineering and construction fields.